The 3rd Generation Partnership Project (referred to as 3GPP) Evolved Packet System (referred to as EPS) consists of Evolved Universal Terrestrial Radio Access Network (referred to as the E-UTRAN), Mobility Management Entity (referred to as MME), serving gateway (referred to as S-GW), Packet Data Network Gateway (referred to as P-GW or PDN GW), Home Subscriber Server (referred to as HSS), 3GPP Authentication, Authorization and Accounting (referred as AAA) server, Policy and Charging Rules Function (referred to as PCRF) entity and other support nodes.
FIG. 1 is an architectural diagram of an EPS system according to the related art. As shown in FIG. 1, the MME is responsible for control plane related work such as mobility management, processing non-access layer signaling, and managing user mobility management context; the S-GW is an access gateway device connected with the E-UTRAN, forwards data between the E-UTRAN and the P-GW, and is responsible for buffering the paging wait data; the P-GW is a border gateway of the EPS and the packet data network (referred to as PDN), and is responsible for the PDN access, forwarding data between the EPS and the PDN, and other functions; both the S-GW and the P-GW are gateways in the core network; the PCRF is a policy and charging rules function entity, and is connected to the operator's Internet Protocol (referred to as IP) traffic network via the receiving interface Rx, and accesses the traffic information, in addition, it is connected with the gateway devices in the network via the Gx/Gxa/Gxc interfaces, and is responsible for initiating an IP bearer establishment, ensuring the Quality of Service (referred to as QoS) of the traffic data, and performing charging control.
The EPS supports interworking with a non-3GPP system, wherein the interworking with the non-3GPP system is implemented through the interface S2a/b/c, and the P-GW works as an anchor point between the 3GPP and non-3GPP systems. In the EPS system architectural diagram, the non-3GPP system is divided into trusted non-3GPP IP access and untrusted non-3GPP IP access. The trusted non-3GPP IP access may directly connect to the P-GW via the S2a Interface; the untrusted non-3GPP IP access needs to connect to the P-GW via an Evolved Packet Data Gateway (referred to as ePDG, since it is an untrusted access, the ePDG at this point is primarily responsible for security), and the interface between the ePDG and the P-GW is S2b; and S2c provides user plane related control and mobility support between the User Equipment (referred to as UE) and the P-GW, and its supporting mobility management protocol is the Mobile IPv6 Support for Dual Stack Hosts and Routers (referred to as DSMIPv6).
In the EPS system, the Policy and Charging Enforcement Function (referred to as PCEF) entity exists in the P-GW, and the PCRF and P-GW exchange information via the Gx interface (see FIG. 1). When the interface between the P-GW and S-GW is based on PMIPv6, the S-GW also has a Bearer Binding and Event Report Function (referred to as the BBERF) entity to perform QoS control on the traffic data flow, and the S-GW and the PCRF exchange information through the Gxc interface (see FIG. 1). When accessing through the trusted non-3GPP access system, the trusted non-3GPP access gateway also has the BBERF. The trusted non-3GPP access gateway and the PCRF exchange information via the Gxa interface (see FIG. 1). When the UE is roaming, the S9 interface works as an interface between the home PCRF and the visited PCRF, meanwhile provides the UE with traffic Application Function (referred to as AF), and sends the PCRF via the Rx interface the traffic information for developing policy and charging control (PCC) policy. In the 3GPP, the corresponding PDN network can be found through the Access Point Name (referred to as APN). Generally, a connection from the UE to the PDN is called as an IP connectivity access network (referred to as IP-CAN) session. In a process of establishing the IP-CAN session, the BBERF and the PCEF respectively establish Diameter sessions with the PCRF, and the Diameter sessions are used to send the policy and charging information for controlling the IP-CAN session and information for developing the policy.
The corresponding BBF (Broadband Forum) proposed a broadband policy control architecture BPCF (Broadband Policy Control Function), specifically as shown in FIG. 2, the BPCF's main function is to develop appropriate policies; the PEP (Policy Enforcement Point) usually resides in a fixed network transmission equipment, such as BRAS (Broadband Remote Access Server)/BNG (Broadband Network Gateway), and executes in accordance with the appropriate policies developed by the BPCF; the AAA stores user's subscription information; the AF (Application Function) develops policies for the BPCF, and provides the corresponding traffic information. Currently the BPCF architecture is still relatively sketchy, and further details are still under development.
Nowadays, the operators are very interested in the FMC (Fixed Mobile Convergence,) scenario, that is, research based on the 3GPP and BBF interoperability. Especially for some large-scale operators having both mobile and fixed broadband networks, such operators want to be able to provide users with unified policy control, allowing users to have consistent service experience after accessing through different accessing ways (for example, 3GPP access in the mobile network, and WLAN access in the fixed network). In order to provide a unified policy control, there is also a need for the convergence of the PCRF (a policy entity for which a mobile network provides control) and the BPCF (a policy entity for which a fixed broadband network provides policy control). Since the current BBF forum does not specify how to implement the BPCF, while there are plans to use the PCRF to achieve the BPCF function in the 3GPP forum, the subsequent converged policy control entity is named as PCRF hereinafter.
When a user develops a service, the user can selectively route the data back to the EPC network, or directly send the data out through the local fixed network transmission equipment BRAS/BNG. The scenarios in which the user accesses the mobile core network via the BBF fixed network (such as WLAN access) can be divided into three categories: 1. untrusted S2b access, wherein, as shown in FIG. 3, the UE accesses via a fixed network equipment, and an IP-Sec tunnel is established between the UE and the ePDG (ePDG acting as a security gateway) for data transmission, and then the UE accesses the EPS core network through the ePDG, the S2b interface between the ePDG and the P-GW can use the PMIP (Proxy Mobile IP) or the GTP (GPRS Tunneling Protocol), and there may be a Gxb* interface (the user of this interface transfers the tunnel information of user access) existing between the ePDG and the PCRF; 2. untrusted S2c access, wherein, as shown in FIG. 4, in this case the DSMIP tunnel is used between the UE and the P-GW, and there is also one layer of IP-Sec tunnel encapsulated in the outer layer of the DSMIP tunnel which is between the UE and the ePDG, and there is no tunnel between the ePDG and the P-GW at this point; 3. trusted S2c access, wherein, as shown in FIG. 5, in this case, it is still the DSMIP tunnel between the UE and the P-GW, but since it is a trusted access relationship, no ePDG exists at this time.
When the UE roams to a visited network, there are two methods for the traffic to be routed to the EPC core network: Home Routed (FIGS. 6a, 6b, 6c) and Local Breakout (FIGS. 7a, 7b, 7c), and the difference is whether the P-GW's location is in the home network or the visited network. In a WLAN Offload connection, however, this part of data are always routed out through the BRAS/BNG in the visited network.
In the case that both the WLAN Offload data and the data routed back to the EPC network exist in this roaming scenario, there is no solution to distinguish these two parts of data in the prior art, thus charging and policy control cannot be performed for these two kinds of data.